SB 6.12.4
chinnaika-bahuh parighena vrtrah
samrabdha asadya grhita-vajram
hanau tatadendram athamarebham
vajram ca hastan nyapatan maghonah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Although one of his arms was severed from his body, Vrtrasura angrily approached King Indra and struck him on the jaw with an iron mace. He also struck the elephant that carried Indra. Thus Indra dropped the thunderbolt from his hand.